1. Field
The present disclosure relates generally to multi-port amplifiers. More particularly, the present disclosure relates to a method and apparatus for improving the leakage performance of a multi-port amplifier.
2. Background
Communications systems oftentimes generate signals that require amplification to high levels of power. As one illustrative example, a geostationary communications satellite that receives multiple signals in various uplink beams over multiple channels may retransmit those signals in various downlink beams amplified to high power. In some cases, these signals may be amplified by assigning one amplifier set at a fixed maximum power level to each signal that is received.
However, in some cases, it is desirable to dynamically allocate a total available pool of power among the various signals. Multi-port amplifiers (MPAs) allow this type of dynamic distribution of power.
A multi-port amplifier receives n component signals as n input signals at an input hybrid network. The input hybrid network rearranges the input signals such that the outputs of the network form an orthogonal transformation of the inputs. Each output of the input hybrid network may be referred to as a composite signal, which is the sum of a phase-shifted version of each and every input signal. For n input signals, the input hybrid network may output n composite signals.
The multi-port amplifier may also include n individual high-power amplifiers, each of which is used to amplify a corresponding composite signal. An output hybrid network is used to perform a generalized inverse transformation of the input hybrid network to separate the various composite signals back into n composite signals, each of which is amplified.
In this manner, each input signal fed into the multi-port amplifier may be amplified using any amount of the total available pool of power. The amount of power distributed to each amplified component signal output from the multi-port amplifier may be proportional to the relative power of the input signals.
For a multi-port amplifier to function properly, the input hybrid network, the output hybrid network, the high-power amplifiers, and all transmission lines connecting these components may need to be aligned in amplitude and phase within selected tolerances. Misalignment of any of the components in the multi-port amplifier may result in incomplete separation of the component signals at the output of the multi-port amplifier. In other words, the misalignment may result in leakage of the various signals across two or more of the output ports of the multi-port amplifier. This leakage may create interference with respect to the intended signals. This interference may deter the use of such multi-port amplifiers.
Some currently available multi-port amplifiers use equalizers to provide amplitude and/or phase adjustments to the composite signals prior to the composite signals being amplified by the high-power amplifiers. However, these equalizers may require special test signals and/or multiple iterations in order to reduce leakage to within selected tolerances. Further, in some cases these equalizers may be unable to reduce leakage to within selected tolerances. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.